Differential cell sensitivity between OTA and LPS upon releasing TNF-α

Mechanoregulation of Osteoclastogenesis-Inducing Potentials of Fibrosarcoma Cell Line by Substrate Stiffness

A micro-physiological system is generally fabricated using soft materials, such as polydimethylsiloxane silicone (PDMS), and seeks an inflammatory osteolysis model for osteoimmunological research as one of the development needs. Microenvironmental stiffness regulates various cellular functions via mechanotransduction. Controlling culture substrate stiffness may help spatially coordinate the supply of osteoclastogenesis-inducing factors from immortalized cell lines, such as mouse fibrosarcoma L929 cells, within the system. Herein, we aimed to determine the effects of substrate stiffness on the osteoclastogenesis-inducing potential of L929 cells via cellular mechanotransduction. L929 cells showed increased expression of osteoclastogenesis-inducing factors when cultured on type I collagen-coated PDMS substrates with soft stiffness, approximating that of soft tissue sarcomas, regardless of the addition of lipopolysaccharide to augment proinflammatory reactions. Supernatants of L929 cells cultured on soft PDMS substrates promoted osteoclast differentiation of the mouse osteoclast precursor RAW 264.7 by stimulating the expression of osteoclastogenesis-related gene markers and tartrate-resistant acid phosphatase activity. The soft PDMS substrate inhibited the nuclear translocation of YES-associated proteins in L929 cells without reducing cell attachment. However, the hard PDMS substrate hardly affected the cellular response of the L929 cells. Our results showed that PDMS substrate stiffness tuned the osteoclastogenesis-inducing potential of L929 cells via cellular mechanotransduction.

Peptide nanotube loaded with a STING agonist, c-di-GMP, enhance cancer immunotherapy against melanoma

The activation of the stimulating factor of the interferon gene (STING) pathway can enhance the immune response within the tumor. Cyclic diguanylate monophosphate (c-di-GMP) is a negatively charged, hydrophilic STING agonist, however, its effectiveness is limited due to the poor membrane permeability and low bioavailability. Herein, we introduced KL-7 peptide derived from Aβ amyloid fibrils that can self-assemble to form nanotubes to load and deliver c-di-GMP, which significantly enhanced c-di-GMP's effectiveness and then exhibited a robust "in situ immunity" to kill melanoma cells. KL-7 peptide nanotube, also called PNT, was loaded with negatively charged c-di-GMP via electrostatic interaction, which prepared a nanocomposite named c-di-GMP-PNT. Treatment of RAW 264.7 cells (leukemia cells in mouse macrophage) with c-di-GMP-PNT markedly stimulated the secretion of IL-6 and INF-β along with phospho-STING (Ser365) protein expression, indicating the activation of the STING pathway. In the unilateral flank B16-F10 (murine melanoma cells) tumor-bearing mouse model, compared to PNT and c-di-GMP, c-di-GMP-PNT can promote the expression of INF-β, TNF-α, IL-6, and IL-1β. At the same time, up-regulated CD4 and CD8 active T cells kill tumors and enhance the immune response in tumor tissues, resulting in significant inhibition of tumor growth in tumor-bearing mice. More importantly, in a bilateral flank B16-F10 tumor model, both primary and distant tumor growth can also be significantly inhibited by c-di-GMP-PNT. Moreover, c-di-GMP-PNT demonstrated no obvious biological toxicity on the main organs (heart, liver, spleen, lung, and kidney) and biochemical indexes of mice. In summary, our study provides a strategy to overcome the barriers of free c-di-GMP in the tumor microenvironment and c-di-GMP-PNT may be an attractive nanomaterial for anti-tumor immunity.

Electronic Supplementary Material

Supplementary material (synthesis and characterization of KL-7 peptide; the encapsulation rate and cumulative release rate of c-di-GMP-PNT; cytotoxicity of PNT, c-di-GMP, and c-di-GMP-PNT; anti-tumor effect of c-di-GMP-PNT (equivalent to 1 and 5 µg c-di-GMP per mouse); representative immunofluorescence images; and biosafety analysis) is available in the online version of this article at 10.1007/s12274-022-5102-z.

A Newly Isolated Alcaligenes faecalis ANSA176 with the Capability of Alleviating Immune Injury and Inflammation through Efficiently Degrading Ochratoxin A

Ochratoxin A (OTA) is one of the most prevalent mycotoxins that threatens food and feed safety. Biodegradation of OTA has gained much attention. In this study, an Alcaligenes faecalis strain named ANSA176, with a strong OTA-detoxifying ability, was isolated from donkey intestinal chyme and characterized. The strain ANSA176 could degrade 97.43% of 1 mg/mL OTA into OTα within 12 h, at 37 °C. The optimal levels for bacterial growth were 22–37 °C and pH 6.0–9.0. The effects of ANSA176 on laying hens with an OTA-contaminated diet were further investigated. A total of 36 laying hens were assigned to three dietary treatments: control group, OTA (250 µg/kg) group, and OTA + ANSA176 (6.2 × 10⁸ CFU/kg diet) group. The results showed that OTA decreased the average daily feed intake (ADFI) and egg weight (EW); meanwhile, it increased serum alanine aminopeptidase (AAP), leucine aminopeptidase (LAP), β2-microglobulin (β2-MG), immunoglobulin G (IgG), tumor necrosis factor-α (TNF-α), and glutathione reductase (GR). However, the ANSA176 supplementation inhibited or attenuated the OTA-induced damages. Taken together, OTA-degrading strain A. faecalis ANSA176 was able to alleviate the immune injury and inflammation induced by OTA.

Genomic analysis of Fisher F344 rat kidneys from a reproductive study following dietary ochratoxin A exposure

Ochratoxin A (OTA) is a mycotoxin produced by species of Penicillium and Aspergillus, and is found in many commodities including cereal grains, nuts, and coffee. OTA is a renal carcinogen and nephrotoxin at high concentrations, targeting the proximal tubules. This study uses transcriptomics and the previously reported apical data (Bondy et al., 2021) to infer mode-of-action of OTA toxicity in male and female rats exposed to low doses of OTA in utero and throughout development. Our findings support a male-specific activation of the innate and adaptive immune responses in F1 pups to OTA exposure. This was not found in the female F1 pups, and may be due to female-specific increased p38 activity and VDR signaling. Differentially expressed genes related to karyomegaly, MAPK activity, and immune activation appears to develop from in utero exposure to OTA whereas those related to decreased kidney and liver function, and changes to reproductive pathways occur in both rat generations. Together, these transcriptional results confirm that dietary exposure to OTA causes renal toxicity as well as alterations to hepatic and reproductive pathways in rats. In utero exposure of rats to OTA results in sex-specific alterations in immune response pathways, VDR signaling, and p38 activity.

Corticosterone potentiates ochratoxin A-induced microglial activation

Microglial activation in the central nervous system (CNS) has been associated with brain damage and neurodegenerative disorders. Ochratoxin A (OTA) is a mycotoxin that occurs naturally in food and feed and has been associated with neurotoxicity, while corticosteroids are CNS’ physiological function modulators. This study examined how OTA affected microglia activation and how corticosteroids influenced microglial neuroinflammation. Murine microglial cells (BV-2) were stimulated by OTA, and the potentiation effects on OTA-induced inflammation were determined by corticosterone pre-treatment. Expressions of pro-inflammatory mediators including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) were determined. Phosphorylation of mitogen-activated protein kinases (MAPKs) was analyzed by western blotting. OTA significantly increased the mRNA expression of IL-6, TNF-α, IL-1β, and iNOS and also elevated IL-6 and NO levels. Corticosterone pre-treatment enhanced the neuroinflammatory response to OTA in a mineralocorticoid receptor (MR)-dependent mechanism, which is associated with increases in extracellular signal-regulated kinase (ERK) and p38 MAPK activation. In response to OTA, microglial cells produced pro-inflammatory cytokines and NO, while corticosterone increased OTA-induced ERK and p38 MAPK phosphorylation via MR. Findings indicated the direct role of OTA in microglia activation and neuroinflammatory response and suggested that low corticosterone concentrations in the brain exacerbated neurodegeneration.

Risk assessment of ochratoxin A in food

The European Commission asked EFSA to update their 2006 opinion on ochratoxin A (OTA) in food. OTA is produced by fungi of the genus Aspergillus and Penicillium and found as a contaminant in various foods. OTA causes kidney toxicity in different animal species and kidney tumours in rodents. OTA is genotoxic both in vitro and in vivo; however, the mechanisms of genotoxicity are unclear. Direct and indirect genotoxic and non-genotoxic modes of action might each contribute to tumour formation. Since recent studies have raised uncertainty regarding the mode of action for kidney carcinogenicity, it is inappropriate to establish a health-based guidance value (HBGV) and a margin of exposure (MOE) approach was applied. For the characterisation of non-neoplastic effects, a BMDL 10 of 4.73 μg/kg body weight (bw) per day was calculated from kidney lesions observed in pigs. For characterisation of neoplastic effects, a BMDL 10 of 14.5 μg/kg bw per day was calculated from kidney tumours seen in rats. The estimation of chronic dietary exposure resulted in mean and 95th percentile levels ranging from 0.6 to 17.8 and from 2.4 to 51.7 ng/kg bw per day, respectively. Median OTA exposures in breastfed infants ranged from 1.7 to 2.6 ng/kg bw per day, 95th percentile exposures from 5.6 to 8.5 ng/kg bw per day in average/high breast milk consuming infants, respectively. Comparison of exposures with the BMDL 10 based on the non-neoplastic endpoint resulted in MOEs of more than 200 in most consumer groups, indicating a low health concern with the exception of MOEs for high consumers in the younger age groups, indicating a possible health concern. When compared with the BMDL 10 based on the neoplastic endpoint, MOEs were lower than 10,000 for almost all exposure scenarios, including breastfed infants. This would indicate a possible health concern if genotoxicity is direct. Uncertainty in this assessment is high and risk may be overestimated.

Long-Time Instead of Short-Time Exposure in Vitro and Administration in Vivo of Ochratoxin A Is Consistent in Immunosuppression

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium, contaminating in a wide variety of foods and feeds. Mycotoxins, including OTA, could cause immunosuppression in almost all previous studies in vivo. However, the vast majority of results in vitro showed that mycotoxins caused immunostimulation. Why the results of studies in vitro are contrary to studies in vivo is unknown. Our study aims to explore the underlying reason and mechanism of the paradoxical effect. In this study, porcine alveolar macrophage cell line 3D4/21 was chosen as an in vitro model and treated with 1.0 μg/mL OTA for different times. Some indexes, such as expression of inflammatory cytokines, migration, phagocytosis, macrophage polarization, autophagy-related proteins, and Akt1 phosphorylation, were detected. The results showed that pro-inflammatory cytokine expression, migration, and phagocytosis were increased, with macrophage polarization to the M1 phenotype at 24 h of OTA exposure. Surprisedly, anti-inflammatory cytokine expression was increased, cell phagocytosis and migration were decreased, and macrophage polarization was switched from M1 to M2 at 72 h of OTA exposure. Furthermore, we found that long-time exposure of OTA also suppressed autophagy, and the autophagy activator blocked the OTA-induced immunosuppression. Phosphorylation of Akt1 plays a positive role in autophagy inhibition. In conclusion, long-time instead of short-time exposure of OTA in vitro induced immunosuppression. The immunosuppression mechanism of OTA in vitro involved inhibition of autophagy through upregulating p-Akt1. Our results provide new insight into research on the mechanism of mycotoxin-induced immunosuppression in vitro.

Effects of curcumin on performance, antioxidation, intestinal barrier and mitochondrial function in ducks fed corn contaminated with ochratoxin A

Curcumin has been attributed with antioxidant, anti-inflammatory, antibacterial activities, and has shown highly protective effects against enteropathogenic bacteria and mycotoxins. Ochratoxin A (OTA) is one of the major intestinal pathogenic mycotoxins. The possible effect of curcumin on the alleviation of enterotoxicity induced by OTA is unknown. The effects of dietary curcumin supplementation on OTA-induced oxidative stress, intestinal barrier and mitochondrial dysfunctions were examined in young ducks. A total of 540 mixed-sex 1-day-old White Pekin ducklings with initial BW (43.4±0.1 g) were randomly assigned into controls (fed only the basal diet), a group fed an OTA-contaminated diet (2 mg/kg feed), and a group fed the same OTA-contaminated feed plus 400 mg/kg of curcumin. Each treatment consisted of six replicates, each containing 30 ducklings and treatment lasted for 21 days. There was a significant decrease in average daily gain (ADG) and increased feed : gain caused by OTA (P<0.05); curcumin co-treatment prevented the decrease in BW and ADG compared with the OTA group (P<0.05). Histopathological and ultrastructural examination showed clear signs of enterotoxicity caused by OTA, but these changes were largely prevented by curcumin supplementation. Curcumin decreased the concentrations of interleukin-1β, tumor necrosis factor-α and malondialdehyde, and increased the activity of glutathione peroxidase induced by OTA in the jejunal mucosa of ducks (P<0.05). Additionally, curcumin increased jejunal mucosa occludin and tight junction protein 1 mRNA and protein levels, and decreased those of ρ-associated protein kinase 1 (P<0.05). Notably, curcumin inhibited the increased expression of apoptosis-related genes, and downregulated mitochondrial transcription factors A, B1 and B2 caused by OTA without any effects on RNA polymerase mitochondrial (P<0.05). These results indicated that curcumin could protect ducks from OTA-induced impairment of intestinal barrier function and mitochondrial integrity.

Stem cell-mediated delivery of SPIO-loaded gold nanoparticles for the theranosis of liver injury and hepatocellular carcinoma

The treatment of liver injuries or hepatocellular carcinoma (HCC) has been hindered by the lack of efficient drug delivery. Even with the help of nanoparticles or other synthetic delivering agents, a large portion of the dose is still sequestered in the reticuloendothelial system. As an alternative, adipose-derived mesenchymal cells (AD-MSCs), which have the capability of homing to the injured liver, can be used as a unique carrier for theranostic agents. Theranostic agents must have the capacity for being non-toxic to host cells during transportation, and for timely activation once they arrive at the injury sites. In this study, we loaded AD-MSCs with superparamagnetic iron oxide-coated gold nanoparticles (SPIO@AuNPs) and tested their effects against liver injury and HCC in cells and in mice. SPIO@AuNP is a non-toxic magnetic resonance (MR)-active contrast agent that can generate heat when irradiated with near-infrared laser. Our results showed that SPIO@AuNPs were successfully transfected into AD-MSCs without compromising either cell viability (P > 0.05) or cell differentiability. In vivo MR imaging and histologic analysis confirmed the active homing of AD-MSCs. Upon laser irradiation, the SPIO@AuNP-loaded AD-MSCs could thermally ablate surrounding HCC tumor cells. SPIO@AuNP-loaded AD-MSCs proved a promising theranostic approach for injured liver and HCC.

Apoptosis induction by OTA and TNF-α in cultured primary rat hepatocytes and prevention by silibinin

In cultures of primary rat hepatocytes, apoptosis occurred after application of 20 ng/mL tumor necrosis factor alpha (TNF-α). However, this was only in the presence of 200 ng/mL of the transcriptional inhibitor actinomycin D (ActD). This toxic effect was completely prevented in the presence of 25 µg/mL soluble TNF-α receptor I (sTNFR I) in the supernatant of hepatocyte cell cultures. Apoptosis also occurred after application of 12.5 µmol/L ochratoxin A (OTA). However, that was not prevented by up to 500 µg/mL sTNFR I, indicating that TNF-α/TNFR I is not involved in OTA mediated apoptosis in hepatocytes. The antioxidative flavanolignan silibinin in doses from 130 to 260 µmol/L prevented chromatin condensation, caspase-3 activation, and apoptotic DNA fragmentation that were induced by OTA, by 10 mmol/L hydrogen peroxide (H₂O₂) and by ultraviolet (UV-C) light (50 mJ/cm²), respectively. To achieve protection by silibinin, the drug was applied to the cell cultures for 2 h in advance. OTA stimulated lipid peroxidation on cultured immortalized rat liver HPCT cells, as was revealed by malondialdehyde (MDA) production. Lipid peroxidation occurred further by H₂O₂ and ActD/TNF-α incubation. These reactions were also suppressed by silibinin pretreatment. We conclude that the anti-apoptotic activity of silibinin against OTA, H₂O₂ and ActD/ TNF-α is caused in vitro by the antioxidative effects of the flavanolignan. Furthermore, cytotoxicity of the pro-apoptotic toxins was revealed by MTT-test. When applied separately, ActD and TNF-α showed no cytotoxic effects after 24 h, but were cytotoxic if applied in combination. The used concentrations of OTA, H₂O₂ and the dose of UV-C caused a substantial decrease in viability within 36 h that was prevented mostly by silibinin. We conclude that silibinin is a potent protective compound against apoptosis and cytotoxicity caused by OTA and the investigated compounds.

High-throughput analysis of tumor necrosis factor signaling pathways in eight cell types during rat hepatic regeneration

This study aims to clarify the relevance of tumor necrosis factor (TNFs) signaling pathways and liver regeneration (LR) at the cellular level. Eight liver cell types were isolated using Percoll density gradient centrifugation and immunomagnetic beads methods. Expressions of TNF signaling pathway-involved genes in each cell type after 2/3 hepatectomy (PH) were detected using gene chip. Results show the following: gene TNFα was upregulated in most cell types, especially in Kupffer cells (KC); TNFβ expression was insignificantly changed in eight liver cell types; the majority of genes involved in four TNFα signaling pathways showed increased expression during LR in hepatocytes (HC); TNFα-induced NFκB pathway-involved genes were upregulated preferentially between 2 and 24 h during LR in biliary epithelial cells (BECs); and TNFα-induced apoptotic pathway genes were downregulated preferentially at progressing phase of LR in dendritic cells (DCs). Referring to the above results, TNFα-mediated signaling pathways, in contrast to TNFβ, play the more proactive role in LR, and four TNFα-mediated signaling pathways seem helpful to regulate biological events in HC; BEC proliferation was partly controlled by TNFα-mediated NFκB pathway; and the impaired TNFα-mediated apoptotic pathway in DCs might contribute to the restoration of DC mass after PH. Briefly, the comparative analysis of genomewide expression profiles of TNF signaling pathways between different cell types is helpful in understanding the implication of TNF signaling in LR at the cellular level.

Silibinin pretreatment protects against ochratoxin A-mediated apoptosis in primary rat hepatocytes

The inhibitory effect of silibinin on ochratoxin A (OTA)-mediated apoptosis on primary rat hepatocytes was investigated. Rat hepatocytes were prepared by two different methods: the classical enzymatic digestion method by collagenase perfusion and a new EDTA-perfusion method. The EDTA-perfusion method yielded hepatocytes, which were stably cultivated without DNA fragmentation for up to 96 h, whereas the collagenase-prepared hepatocytes showed apoptosis events as early as from the start of preparation even in the absence of OTA. Treatment with 12.5 μmol/l OTA of cultured hepatocytes prepared under ETDA perfusion developed DNA-laddering after 24-36 h. Lipopolysaccharide (LPS) of 0.1 up to 12.5 μg/ml showed no apoptotic DNA-effects under these conditions. A low concentration of 26 μmol/l silibinin given prior to OTA slightly prevented OTA-mediated DNA-laddering, whereas a five times higher concentration of silibinin (130 μmol/l) completely inhibited OTA-mediated apoptosis. Under the same conditions, caspase-3 activity in hepatocytes increased in a time-dependent manner under OTA exposure within 12-24 h but was blocked by 130 μmol/l silibinin. In contrast, LPS incubation for 12 and 24 h did not alter caspase-3 activity. To measure viability of OTA-/LPS-treated hepatocytes, the MTT-test and Live/Dead kit were applied. The results demonstrated that the used OTA concentration of 12.5 μmol/l only moderately decreased viability for up to 24 h but showed cytotoxic effects depending on longer incubation times (≥36 h). In contrast, LPS up to 12.5 μg/ml exhibited no cytotoxic effects up to 48 h. In summary, our results showed contrasting effects on apoptosis in primary rat hepatocytes by OTA (produces apoptosis) versus LPS (produces no apoptosis), also depending on the method of hepatocyte preparation. Silibinin at 130 μmol/l showed significant hepatoprotective and antiapoptotic effects against OTA-mediated cell damage on cultured rat hepatocytes.